Find the Difference LeetCode Solution - The Coding Shala

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In this post, we will learn how to solve LeetCode's Find the Difference Problem and will implement its solution in Java.

Find the Difference Problem

You are given two strings s and t. String t is generated by random shuffling string s and then add one more letter at a random position. Return the letter that was added to t.

Example 1:
Input: s = "abcd", t = "abcde"
Output: "e"
Explanation: 'e' is the letter that was added.

Practice this problem on LeetCode.

LeetCode - Find the Difference Java Solution

Approach 1

Using HashMap.

Java Program:

```class Solution {
public char findTheDifference(String s, String t) {
Map<Character, Integer> map = new HashMap<>();
for(int i=0; i<s.length(); i++) {
if(map.containsKey(s.charAt(i))) {
map.put(s.charAt(i), map.get(s.charAt(i))+1);
} else {
map.put(s.charAt(i), 1);
}
}

for(int i=0; i<t.length(); i++) {
if(!map.containsKey(t.charAt(i)) || map.get(t.charAt(i)) == 0) {
return t.charAt(i);
} else {
map.put(t.charAt(i), map.get(t.charAt(i))-1);
}
}
//ignore this return;
return ' ';
}
}
```

Approach 2

Using Bit Manipulation.

If we do xor in both the string only additional char will remain.

Java Program:

```class Solution {
public char findTheDifference(String s, String t) {
char ch = t.charAt(t.length()-1);
for(int i=0; i<s.length(); i++) {
ch ^= s.charAt(i);
ch ^= t.charAt(i);
}
return ch;
}
}
```

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